The proposed project is designed to investigate the posttranscriptional regulation of utilization of stored, maternal messenger RNA templates during early embryonic development. This mRNA is synthesized during oogenesis, and is stored in an inactive form in the egg. After fertilization, the bulk of protein synthesis is directed by these templates. In the proposed study microtubule proteins, which are synthesized as products of these stored mRNA's will be studied since the synthesis of these proteins provides a specific assay for the utilization of a very restricted class of maternal mRNA's. It will be possible to determine the timing of regulation. Further, it will also be possible, by observing the behavior of the microtubule protein synthesizing polyribosomes, to assess the nature of the regulation. Experiments will also be performed on localization of microtubule protein mRNA's in eggs and developing embryos, on the heterogeneity of microtubule protein mRNA's, and upon the general metabolism of these key proteins in early development.